1. Field of the Invention
The present invention relates to a pneumatic oil pump, and more particularly to a pneumatic oil pump for a hydraulic device.
2. Description of Related Art
With reference to FIGS. 8 and 9, a conventional pneumatic motor to drive a hydraulic pump in accordance with the prior art comprises a cylinder (80), a piston (84), a drive rod (86), a spring (88) and a rod base (83). A front cover (81) and a rear cover (82) are respectively used to cover each end of the cylinder (80). An inlet (812) is defined in the front cover (81) to connect to a high-pressure air supply. An outlet (822) is defined in the rear cover (82) to release the air. A recess (802) is defined in the inner surface of the cylinder (80) near the middle position of the cylinder (80).
The piston (84) is movably received in the cylinder (80) so as to divide the cylinder (80) into a first chamber communicating with the inlet (812) and a second chamber communicating with the outlet (822). A seal (841) is mounted around the piston (84) at each end of the piston (84). An inlet passage (842) is defined in the piston (84) between the seals (841). A cavity (844) is defined in the piston (84) and communicates with the inlet passage (842). An outlet passage (846) is defined in the piston (84) and communicates with both chambers of the cylinder (80). An inner piston (90) is movably received in the cavity (844) of the piston (84). A rod (92) is secured to the inner piston (90) and extends into the first chamber of the cylinder (80). A valve disk (94) is secured to the rod (92) to close the passage between the outlet passage (846) and first chamber of the cylinder (80).
The drive rod (86) is attached to the piston (84) and extends into a passage (832) defined in the rod base (83). The spring (88) is mounted between the piston (84) and the rear cover (82) to provide a pushing force to the piston (84), such that the piston (84) abuts the front cover (81) before the pump is in operation. The rod base (33) is connected to an oil reservoir.
In operation, high-pressure air is injected into the first chamber through the inlet (812). The piston (84) is pushed relative to the cylinder (80) by the air pressure. The drive rod (86) moves inward relative to the passage (832), and the spring (88) is compressed. When the piston (84) moves to the position where the seal (841) on the inlet end of the piston (84) is in the recess (802), the air in the first chamber will flow into the cavity (844) in the piston (84) through the recess (802) and the inlet passage (842). The air will move the inner piston (90) relative to the cavity (844), and the valve disk (94) opens to allow the first chamber to communicate with the outlet passage (846). Accordingly, the air in the first chamber will directly flow into the second chamber through the outlet passage (846). The pushing force provided by the air pressure on the piston (84) will reduce. The tension in the compressed spring (88) will move the piston (84) back toward the front cover (81), and the drive rod (86) moves outward relative to the passage (832) in the rod base (83). When the valve disk (94) strikes the front cover (81), the valve disk (94) is pushed toward the piston (84) and closes the passage between the first chamber and the outlet passage (846). Consequently, the high-pressure air pushes the piston (84) toward the rear cover (82) again. Accordingly, a suction force will be applied to the oil in the oil reservoir as the drive rod (86) moves backward and pressure will be applied to the oil in the passage (832) as the drive rod moves forward. With the appropriate use of a series of valves, the oil can be transmitted to a hydraulic device like a power repairing kit, a hoisting jack, a hydraulic cylinder, a hydraulic jack or the like.
However, the conventional pneumatic motor for a hydraulic pump has the following disadvantages:
1. Noise and shock easily occur when the high-pressure air is released through the outlet passage (846).
2. Noise occurs when the valve disk (94) strikes the front cover (81).
3. Dust easily enters the cylinder (80) through the outlet (822), such that the inner elements of the pneumatic motor are easily worn out. The useful life of the pneumatic motor is shortened.
To overcome the shortcomings, the present invention tends to provide an improved pneumatic motor for a hydraulic pump to mitigate or obviate the aforementioned problems.
The main objective of the invention is to provide an improved pneumatic oil pump that can reduce the noise generated by the pneumatic motor. The pneumatic oil pump comprises a cylinder, a piston, a pedal and an oil reservoir. The cylinder has a central bore, a sealed front end and a sealed rear end. An air connector is mounted on the front end of the cylinder. An actuating valve is mounted on the front end of the cylinder and communicates with the air connector and the central bore of the cylinder. The piston is movably mounted in the bore to divide the central bore into a first chamber and a second chamber. A piston seat is attached to the piston on the end facing the rear end of the cylinder. A ventilative, sound-absorbing material is mounted between the air outlets of the piston and the piston seat. With such a ventilative, sound absorbing material, noise will not occur when the air releases from the cylinder.
The secondary objective of the invention is to provide an improved pneumatic oil pump wherein an exhaust valve is mounted on the cylinder and communicates with the second chamber in the cylinder. Consequently, dust cannot enter the cylinder. Wear of the inner elements can be significantly reduced, and the useful life of the pneumatic oil pump is prolonged.
The third objective of the invention is to provide an improved pneumatic oil pump wherein a pushing rod is slidably mounted on the front end of the cylinder and communicates with the air connector. With such a pushing rod, the impact between the piston and the front end of the cylinder can be cushioned. Noise will not occur when the air pump is in operation.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.